The present invention relates generally to improvements in fuel cell fuel delivery arrangements for use in combustion tools, and more specifically to adapters provided to combustion tool fuel cells for obtaining more consistent fuel dosing.
In the present application the term “combustion nailer” refers to combustion powered fastener driving tools, also known as fastener drivers, combustion tools, cordless framing tools, cordless trim tools and the like. More particularly, the present invention relates to improvements in the delivery of fuel from fuel cells customarily provided for such purposes.
Such tools typically have a housing substantially enclosing a combustion power source, a fuel cell, a battery, a trigger mechanism and a magazine storing a supply of fasteners for sequential driving. The power source includes a reciprocating driver blade which separates a forward most fastener from the magazine and drives it through a nosepiece into the workpiece. Exemplary tools are described in U.S. Pat. Nos. 4,483,473; 4,522,162; 6,145,724; and 6,679,414, all of which are incorporated by reference. Such fastener-driving tools and such fuel cells are available commercially from ITW-Paslode (a division of Illinois Tool Works, Inc.) of Vernon Hills, Ill., under its IMPULSE trademark.
As exemplified in Nikolich U.S. Pat. Nos. 4,403,722; 4,483,474; and 5,115,944, all of which are also incorporated by reference, it is known to use a dispenser such as a fuel cell to dispense a hydrocarbon fuel to a combustion tool. A design criterion of such fuel cells is that only a desired amount of fuel or dose of fuel should be emitted by the fuel cell for each combustion event. The amount of fuel should be carefully monitored to provide the desired combustion, yet in a fuel-efficient manner to prolong the working life of the fuel cell.
Prior attempts to address this dosage factor have resulted in fuel metering valves located in the tool (U.S. Pat. No. 5,263,439) or attached to the fuel cell (U.S. Pat. No. 6,302,297), both of which are also incorporated by reference. Fuel cells have been introduced having internal metering valves, as disclosed in U.S. Pat. No. 7,392,922, also incorporated by reference. Other combustion tool fuel delivery arrangements are disclosed in U.S. Pat. Nos. 7,478,740; 7,571,841; 7,591,249; 7,654,429; and 7,661,568, all of which also being incorporated by reference.
Regardless of the location of the metering valve, the associated combustion nailer is designed to exert a force on the valve, either the reciprocating valve stem or on the valve body itself, to cause the stem to retract against a biasing force in the metering valve to dispense a measured dose of fuel. It is important for fuel economy in the fuel cell, and for desired operation of the combustion nailer, that only the designated amount of fuel to be supplied to the tool on a dosage basis.
Designers of such tools are focused on maintaining a sealed relationship in the fuel delivery system for more efficiently using fuel in the fuel cells, and in particular when the tool is used at relatively cooler ambient temperatures (below about 50° F., 10° C.). Another drawback of conventional systems is that when the fuel cell stem is provided with an adapter extension, in some cases the fuel cell stem is exposed to external accidental contacts. Such external accidental contacts may unintentionally dispense fuel, or damage or even break the fuel stem, leaving the fuel cell unusable.
Another factor faced by designers of such tools relates to an inherent aspect of manufactured plastic parts, known as tolerance buildup. Components need to be designed to accommodate a range of dimensions for various components to account for manufacturing tolerances. In the present operational environment, the engagement between the fuel cell valve stem and the corresponding fuel delivery components and passages of the tool needs to be maintained in a positive, fluid communicative relationship, while both preventing leaks and also while accommodating such dimensional component variations. In addition, the fuel delivery system should also be designed to maintain the fuel flow in the face of severe impact forces generated in the combustion process.